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XLhc  Taniversit?  of  Chicago 

FOUNDED  BY  JOHN  D  ROCKEFELLFR 

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THE  YERKES  OBSER  V 

WILLIAMS  BAY,  WISCONSInV>  ^ 


THE  UNIVERSITY  OF  CHICAGO  PRESS 
CHICAGO,  ILLINOIS 


Fig.  I. — The  Yerkes  Observatory  from  the  Northwest 


THE  YERKES  OBSERVATORY 

By  Edwin  Brant  Frost,  Director 

The  establishment  of  a  large  observatory  for  astrophysical  research  in 
connection  with  the  University  of  Chicago  was  the  conception  of  George  E. 
Hale,  who  had  achieved  success  in  his  solar  work  with  his  private  equipment  in 
Chicago,  known  as  the  Kenwood  Observatory.  President  Harper  took  an 
active  interest  in  the  realization  of  the  plan,  which  presently  took  shape  as  an 
opportunity  occurred  for  the  purchase  of  two  very  perfect  glass  disks  (crown  and 
flint)  of  42  inches  diameter,  sufficient  for  the  construction  of  an  object-glass 
of  40  inches  clear  aperture.  These  disks  had  been  cast  by  the  well-known 
makers  of  optical  glass,  Mantois  of  Paris,  upon  order  of  an  institution  in  south¬ 
ern  California,  which  was,  however,  then  unable  to  raise  the  money  for  figuring 
and  mounting  the  telescope.  The  opportunity  was  presented  by  Dr.  Harper 
and  Mr.  Hale  to  Mr.  Charles  T.  Yerkes,  a  keen  business  man  of  Chicago,  of 
purchasing  these  disks  and  securing  the  largest  refracting  telescope  in  the  world. 
Mr.  Yerkes  agreed  in  September,  1892,  to  finance  the  undertaking,  and  a  con¬ 
tract  was  made  with  the  famous  firm  of  Alvan  Clark  &  Sons,  of  Cambridge- 
port.  Mass.,  for  figuring  the  two  disks,  which  were  then  in  their  hands,  and  with 
Warner  &  Swasey,  of  Cleveland,  Ohio,  for  constructing  a  suitable  mounting. 

Mr.  Hale  was  appointed  director  of  the  new  institution,  and  gave  much 
study  to  the  plans  for  the  instruments  and  building.  He  outlined  in  October, 
1892,  the  principal  lines  of  scientific  work  which  would  be  undertaken. 

The  site  of  the  observatory  was  selected  after  a  careful  investigation  of  the 
available  locations  and  after  an  expression  of  opinion  had  been  obtained  from 
numerous  astronomers  familiar  with  large  telescopes.  On  account  of  the 
smokiness,  dust,  and  jar,  as  well  as  the  glare  due  to  the  lights  of  a  great  city,  it 
was  at  once  obvious  that  the  observatory  ought  not  to  be  established  within  or 
near  the  limits  of  Chicago.  But  by  reason  of  its  connection  with  the  Uni¬ 
versity  it  was  practically  essential  that  it  should  not  be  placed  more  than  one 
hundred  miles  away  from  the  other  departments  of  the  University.  Tracts 
of  land  were  offered  in  more  than  twenty  places  in  Illinois  and  elsewhere,  but 
the  situation  on  Lake  Geneva  seemed  to  offer  the  advantages  of  freedom  from 
disturbance  by  commerce,  present  or  prospective,  and  from  the  encroach¬ 
ment  of  too  numerous  dwellings,  together  with  sufficient  accessibility  from 
the  University  and  city.  The  site  of  53  acres  was  presented  by  Mr.  John 
Johnston,  Jr.;  other  adjacent  land  was  later  acquired  by  the  Trustees  of  the 
University,  so  that  since  1907  the  grounds  have  included  about  70  acres,  with 
a  frontage  of  550  feet  on  the  lake  (where  a  pier  for  steamers  is  maintained  in 
summer). 


3 


4 


THE  UNIVERSITY  OF  CHICAGO 


Fig.  2. — The  40-iNCH  Refractor,  Taken  with  the  Rising  Floor  Nearly  at  Its 

Lowest  Point 

The  Observatory  is  situated  about  190  feet  above  the  level  of  the  lake,  or 
1,050  feet  above  the  sea.  Its  geographical  position,  as  determined  by  officers  of 
the  United  States  Coast  and  Geodetic  Survey  in  1900,  is:  Latitude,  42°  34' 
12^64;  Longitude,  5^  54“  13^24  west  of  Greenwich.  The  grounds  are  one  mile 
from  the  post-office  of  the  little  village  of  Williams  Bay,  Wisconsin,  and  a 


THE  YERKES  OBSERVATORY 


5 


mile  and  a  quarter  from  the  station,  at  the  terminus  of  a  branch  of  the  Chicago 
&  Northwestern  Railway,  76  miles  from  Chicago.^ 

In  the  summers  of  1907  and  1908  a  beginning  was  made  in  grading  the 
grounds  of  the  Observatory  after  a  plan  designed  by  Olmsted  Bros.,  of  Brook¬ 
line,  Massachusetts.  Further  work  in  grading  and  planting  was  done  in  1913. 
When  the  original  plan  is  completed  and  the  planting  has  been  carried  out 
as  proposed,  an  appropriate  setting  will  be  secured  for  the  architecturally 
impressive  building. 

The  Observatory  was  designed  by  Henry  Ives  Cobb,  who  carried  out  the 
plans  drawn  up  by  Professor  Hale  in  a  way  that  successfully  combined  archi¬ 
tectural  effect  with  scientific  utility.  The  large  observatories  of  America  and 
Europe  were  visited  by  Mr.  Hale  before  the  plans  were  begun,  the  most  useful 
suggestions  being  received  from  the  designs  of  the  Lick  Observatory  and  the 
Astrophysical  Observatory  at  Potsdam,  Prussia.  The  style  of  the  building  is 
Romanesque  with  rather  elaborate  details.  It  is  constructed  of  brown  Roman 
brick,  with  terra-cotta  ornaments  to  match.  The  shape  is  that  of  a  Latin 
cross,  with  the  three  towers  and  the  meridian  room  at  the  extremities.  The 
long  axis  lies  east  and  west,  with  the  great  tower  at  the  west,  92  feet  in  diameter. 
The  entire  length  of  the  building  in  this  direction  is  326  feet.  The  two  smaller 
domes  are  on  the  north -and-south  axis,  with  their  centers  144  feet  apart. 

The  basement  floor  contains  the  instrument  shop,  the  machine  shop,  a  car¬ 
penter  shop,  a  large  physical  laboratory  adjoining  a  room  fitted  with  a  Rowland 
concave  grating,  and  several  dark  rooms  for  photographic  work.  The  main 
floor  contains  seven  offices  for  the  staff,  a  laboratory,  computing  room,  and 
lecture-room,  a  reception  room  for  women,  a  library  40X20  feet,  besides  dark 
rooms,  chemical  laboratory,  and  cabinets  for  instruments.  The  low  attic  is 
used  for  a  stackroom  for  books  and  for  storage,  and  an  important  room  called 
the  heliostat  room,  nearly  100  feet  long,  is  provided  on  the  second  floor  between 
the  smaller  towers.  At  the  north  end  the  roof  can  be  slid  back  so  that  a  good 
view  of  the  sky  is  obtained,  and  a  heliostat  can  be  mounted  on  the  pier  at  that 
point.  The  horizontal  beam  of  light  can  then  be  studied  in  the  particular 
manner  desired  in  the  long  room,  which  is  provided  with  numerous  piers. 
The  most  important  piece  of  work  thus  far  done  in  this  laboratory  was  the 
first  successful  measurement  of  the  heat  of  the  stars  by  Professor  Ernest  F. 
Nichols  (then  of  Dartmouth  College)  in  the  summers  of  1898  and  1900. 

THE  GREAT  REFRACTOR 

The  forty-inch  telescope  is  mounted  upon  a  massive  brick  pier,  which  rests 
upon  a  solid  concrete  foundation  set  in  the  prevalent  gravel  formation.  The 
column  is  of  cast-iron  in  four  heavy  sections.  The  center  of  motion  of  the 
telescope  is  62  feet  above  the  ground.  The  length  of  the  telescope  is  62  feet, 

•Additional  railway  facilities  are  obtained  by  the  trolley  line  terminating  at  the  head  of  the  lake 
(Fontana),  two  miles  from  the  Observatory,  which  connects  with  the  Chicago,  Milwaukee  &  St.  Paul 
Railway  (Chicago  and  Madison  line)  at  Walworth,  Wisconsin,  and  with  the  Chicago  &  Northwestern 
Railway  (main  line  to  Minneapolis)  at  Harvard,  Illinois,  twelve  miles  distant. 


6 


THE  UNIVERSITY  OF  CHICAGO 


and  spectroscopic  attachments  can  be  added  which  increase  the  length  by 
nearly  lo  feet.  The  instrument  can  be  readily  moved  by  hand  in  spite  of 
the  weight,  6  tons,  of  the  tube,  and  that  (total  20  tons)  of  all  moving  parts. 
Electric  motors  are  available,  however,  by  which  the  instrument  can  be  quickly 
pointed  toward  any  part  of  the  sky.  For  spectroscopic  and  photographic  work 
it  is  necessary  to  correct  the  position  of  the  telescope  by  very  slight  motions, 
for  which  additional  motors,  controlled  by  the  observer’s  hand,  are  provided. 
With  these  the  eye-end  can  be  moved  by  an  amount  as  small  as  xio  inch  and 
stopped  at  the  position  desired.  The  driving-clock,  by  which  the  telescope  is 
made  to  follow  the  stars,  occupies  a  small  room  in  the  top  of  the  pier.  Its 
performance  has  been  remarkably  satisfactory  during  the  twenty-one  years  it  has 
now  been  in  use,  at  temperatures  ranging  from  —25°  F.  to  +90°  F.,  and  under 
great  variations  as  to  humidity.  When  the  driving-weight  reaches  the  end  of 
its  descent  within  the  pier,  it  touches  a  button,  turning  on  a  switch,  and  the 
clock  is  wound  up  by  a  motor.  By  shifting  a  gear  the  rate  of  the  clock  may 
be  changed  to  make  the  telescope  follow  either  the  sun,  or  moon,  or  stars. 
Finely  graduated  circles  were  provided  for  reading  off  the  position  of  the 
telescope,  but  in  practice  the  two  coarse  circles,  five  and  eight  feet  in  diameter, 
with  large  graduations  visible  from  the  floor,  have  been  found  sufficient  and 
quicker  in  operation.  For  sighting  the  instrument  a  finder  of  4  inches  aper¬ 
ture  is  provided,  and  for  the  spectrograph  a  small  finder  of  60  feet  focus, 
without  tube,  is  used. 

The  optical  quality  of  the  telescope  is  of  the  highest  order;  under  favorable 
atmospheric  conditions  very  faint  objects  have  been  seen  with  it  and  close  stars 
separated.  A  German  authority  who  had  investigated  the  quality  of  many 
objectives,  by  means  of  photographs  taken  inside  and  outside  of  the  focus, 
placed  this  at  the  head  of  the  great  lenses  he  had  studied.  A  great  telescope, 
of  long  focal  length,  makes  very  exacting  demands  upon  the  atmosphere,  far 
more  than  is  the  case  with  a  smaller  instrument.  Consequently  a  casual 
visitor  would  very  probably  be  disappointed  not  to  find  a  higher  magnification 
employed  on  an  average  night.  In  a  more  favorable  climate,  such  as  that  of 
California,  the  performance  would  undoubtedly  be  much  better  than  here.^ 
In  the  work  done  with  the  spectrograph  the  steadiness  of  the  air  is  not  of  as 
much  consequence,  as  unfavorable  conditions  merely  protract  the  exposure 
without  injuring  the  quality  of  the  plate.  For  visual  observations  of  objects 
which  are  sufficiently  bright  a  large  iris  diaphragm  has  recently  been  con¬ 
structed  in  the  shop,  by  which  any  desired  part  of  the  whole  aperture  may  be 
used. 

The  operation  of  the  large  telescope  is  greatly  facilitated  by  the  admirable 
arrangements  of  the  dome  and  rising  floor,  designed  and  constructed  by  Warner 
&  Swasey.  In  order  to  have  ample  room  for  attaching  spectroscopes  and  other 

»  Weather  at  Lake  Geneva. — A  record  is  kept  of  the  number  of  hours  during  which  the  40-inch  tele¬ 
scope  is  in  use  at  night.  It  should  be  understood  that  except  for  cloudy  skies  it  is  employed  throughout 
every  night  of  the  year.  In  1908,  a  very  clear  year,  it  was  in  use  during  over  1880  hours,  or  about  52  per 
cent  of  the  total  night  hours.  It  is  doubtful  if  many  European  observatories  could  give  as  good  a  record 
of  clearness. 


THE  YERKES  OBSERVATORY 


7 


apparatus,  it  was  necessary  that  the  dome  should  be  large,  and  its  diameter  is 
90  feet.  It  is  turned  on  36  wheels  by  an  electric  motor  which  actuates  an  end¬ 
less  wire  rope  extending  around  the  whole  dome.  The  controller  is  on  the 
rising  floor  just  at  the  north  side  of  the  pier.  Six  minutes  are  required  for 
turning  the  dome  completely  around.  The  rising  floor  is  75  feet  in  diameter, 
and  is  supported  by  four  cables  running  over  four  sheaves  just  under  the  upper 
balcony  and  connecting  with  heavy  counterpoises  which  balance  a  large  part 
of  the  weight  of  the  floor  (37I  tons).  A  powerful  motor,  with  its  controller 
conveniently  near  to  that  for  turning  the  dome,  supplies  the  power.  The 
floor  moves  through  a  range  of  23  feet  from  the  lower  to  the  upper  balcony. 
It  has  to  be  nearly  at  its  lowest  point  when  an  observer  is  looking  at  a  star  near 
the  zenith.  In  intermediate  positions  the  floor  can  be  quickly  adapted  to 
the  height  of  the  eyepiece  of  the  telescope.  The  opening  in  the  dome  through 
which  the  sky  is  observed  is  ii  feet  wide,  and  it  is  closed  by  shutters  85  feet 
long.  These  are  so  well  constructed  that  they  can  be  very  easily  moved  by 
hand.  Canvas  screens,  which  may  be  raised  over  part  of  the  opening,  serve 
to  break  the  force  of  the  wind. 

ACCESSORIES  AND  LINES  OF  RESEARCH 

The  principal  accessories  of  the  telescope  and  the  lines  of  work  done  with 
each  may  now  be  mentioned.  The  filar  micrometer  is  attached  at  the  eye-end 
for  nearly  all  visual  observations.  It  was  presented  by  Mr.  Yerkes  and  con¬ 
structed  by  Warner  &  Swasey.  It  enables  the  observer  to  determine  very 
exactly  the  angular  separation  of  two  objects  (or  points)  both  of  which  are 
visible  in  the  eyepiece  at  the  same  time,  and  to  fix  the  angle  made  by  the  line 
joining  the  points  with  the  north-and-south  direction.  The  micrometer  has 
during  the  past  twenty  years  been  in  use  for  a  little  more  than  one-half  the  time, 
generally  on  three  or  four  nights  per  week.  With  it  Mr.  Burnham  made  a 
great  number  of  observations,  most  of  which  were  utilized  in  his  monumental 
catalogue  of  double  stars  published  in  1906.  Mr.  Barnard  has  similarly  meas¬ 
ured  with  great  skill  and  persistence  the  positions  of  many  stars  in  a  number  of 
the  star  clusters,  of  the  fainter  satellites  of  our  system,  of  nebulae  and  faint 
comets,  and  has  observed  the  most  important  objects  suitable  for  visual 
examination.  Double  stars  are  now  observed  chiefly  by  Mr.  Van  Biesbroeck. 

A  very  important  method  of  using  the  telescope  as  a  camera  was  successfully 
applied  by  Mr.  G.  W.  Ritchey,  principally  in  1900  and  1901.  The  photographs 
obtained  by  him  of  the  moon,  star  clusters,  and  some  nebulae  were  at  once 
recognized  as  among  the  very  best  thus  far  secured.  For  this  service  there  is 
substituted,  in  place  of  the  eyepiece,  a  plate-holder,  which  can  be  very  delicately 
moved  either  north  and  south  or  east  and  west,  and  can  thus  follow  the  slight 
oscillations  of  the  object  due  to  the  unsteadiness  of  our  atmosphere  during  the 
exposure.  The  crown  and  flint  lenses  of  the  40-inch  objective  were  of  course 
so  figured  as  to  be  achromatic  for  the  rays  to  which  the  eye  is  most  sensitive, 
the  yellow  and  the  green.  By  the  interposition  of  a  color-filter  cutting  down 


8 


THE  UNIVERSITY  OF  CHICAGO 


Fig.  3. — Lunar  Crater  Theophilus  and  Surrounding  Region 

Photographed  with  the  40-inch  refractor  in  less  than  one-half  second  (Ritchey). 
The  diameter  of  the  large  crater  is  64  miles;  its  walls  rise  to  a  height  of  18,000  feet, 
and  the  central  peaks  (notice  their  shadows  cast  toward  the  left)  are  about  6,000 
feet  high. 

the  blue  and  the  violet  rays,  which  are  not  simultaneously  in  focus  with  the 
visual  rays,  and  by  the  use  of  isochromatic  plates,  which  are  sensitized  for  the 
visual  rays,  a  sharp  photograph  is  obtained.  A  negative  of  a  star  cluster  or 
other  object,  secured  in  this  way  when  atmospheric  conditions  are  particularly 
good,  is  then  measured  under  a  microscope  in  the  laboratory,  and  even  weeks 
of  work  can  be  profitably  spent  upon  a  single  fine  negative. 

During  1904  and  1905  a  large  number  of  stellar  photographs  were  thus 
obtained  by  Mr.  Schlesinger,  who  measured  them  most  carefully  in  order  to 
determine  from  the  plates  the  distances  from  the  sun  of  certain  selected  stars. 
The  very  accurate  results  were  published  in  1911.  This  work  has  been  con¬ 
tinued  by  Messrs.  Slocum,  Lee,  Van  Biesbroeck,  and  others. 


THE  YERKES  OBSERVATORY 


9 


Fig.  4. — Mars 

Photographs  made  on  September  28,  1909,  with  40-inch  telescope  (Barnard). 

A  small  lens  takes  the  place  of  the  eyepiece  and  enlarges  the  image  about  three 
times.  Numerous  exposures  of  3  or  4  seconds’  duration  are  made  in  quick  succession 
in  order  to  catch  a  moment  when  the  atmosphere  permits  good  definition. 

Note  the  bright  spot  at  the  left  of  the  top  of  the  pictures:  this  is  the  south  polar 
“cap,”  probably  due  to  snow  in  the  planet’s  polar  regions;  it  diminishes  rapidly  as  the 
planet’s  summer  comes  on  for  that  hemisphere. 

It  is  not  known  what  the  large  dark  regions  represent.  They  were  formerly 
supposed  to  be  oceans,  but  this  idea  is  now  abandoned.  It  is  thought  that  there  are 
no  large  bodies  of  water  on  the  planet.  The  lighter  regions  are  possibly  deserts,  and 
the  dark  ones  are  possibly  due  to  vegetation. 


lO 


THE  UNIVERSITY  OF  CHICAGO 


Another  attachment  of  the  telescope  is  a  stellar  photometer  with  which  the 
brightness  of  the  stars  is  measured.  Observations  of  many  faint  stars  have 
thus  been  made  by  Mr.  Parkhurst,  both  visually  and  photographically. 

About  one-fourth  of  the  nocturnal  hours  of  the  telescope,  generally  two 
nights  per  week,  are  devoted  to  stellar  spectroscopy.  The  instrument,  which 
was  largely  constructed  in  the  shops  of  the  Observatory,  is  designated  as  the 
Bruce  spectrograph,  the  funds  for  its  construction  and  early  operation  having 
been  contributed  by  the  late  Miss  Catherine  W.  Bruce,  of  New  York.  A 
photograph  of  the  spectrum  of  a  star,  accompanied  by  a  comparison  spectrum 
on  the  same  plate  from  metallic  terminals  vaporized  by  the  passage  of  sparks 
from  an  induction  coil  in  the  dome,  can  be  measured  under  a  microscope, 
and  the  speed  of  the  star  in  the  line  of  sight  (on  the  average  about  lo  miles  per 
second)  can  be  inferred  from  the  displacements  of  the  star’s  lines  from  the 
position  of  the  lines  due  to  the  spark.  About  8,000  photographs,  or  spectro¬ 
grams,  have  been  obtained  to  date  with  the  instrument,  chiefly  by  Messrs. 
Frost,  Adams,  Barrett,  and  Lee.  Interesting  results  have  come  from  the 
measurements  of  the  spectrograms,  and  some  200  spectroscopic  binaries,  or 
double  stars  so  close  to  each  other  that  they  can  be  separated  only  in  this 
spectroscopic  manner,  have  been  detected. 

An  especially  important  use  of  the  great  refractor  has  been  in  the  study  of 
the  sun.  The  attachment  generally  used  is  the  spectroheliograph,  so  named  by 
Mr.  Hale,  its  inventor,  when  he  brought  it  into  successful  operation  at  the  Ken¬ 
wood  Observatory. 

The  instrument  regularly  in  use  here  since  1903  is  known  as  the  Rumford 
spectroheliograph.  It  is  a  heavy  spectrograph  (700  lbs.)  with  which,  by  the 
motion  of  the  plate  while  the  sun’s  image  is  passing  across  the  slit,  pictures  of 
the  sun’s  surface  and  surrounding  prominences  may  be  secured  in  monochro¬ 
matic  light,  from  some  one  line  of  calcium,  or  hydrogen,  or  other  element  which 
may  be  particularly  active  on  the  sun.  Adjustments  can  be  so  made  that  the 
photograph  will  depict  either  the  lower,  the  intermediate,  or  the  upper  levels 
of  the  incandescent  vapors  that  lie  above  the  surface.  The  scarlet  radiation  of 
hydrogen  shows  in  a  marked  degree  the  vortices  forming  around  a  sun-spot 
(which  may  be  regarded  as  a  storm  in  the  sun’s  atmosphere) ,  as  was  first  found 
by  Mr.  Hale  with  his  fine  apparatus  installed  on  Mount  Wilson,  California. 
Visual  and  photographic  studies  of  the  sun  are  made  with  other  spectroscopes, 
and  direct  photographs  are  also  taken  with  the  great  telescope.  This  work 
was  carried  on  by  Messrs.  Hale  and  Ellerman  in  1903-4;  then  by  Mr.  Fox; 
from  1909  to  1914  by  Mr.  Slocum,  and  subsequently  by  Mr.  Lee  and  others. 

OTHER  TELESCOPES  AND  APPARATUS 

The  southeast  dome,  30  feet  in  diameter,  contains  the  two-foot  reflector,  an 
instrument  quite  as  powerful  for  some  purposes  as  the  40-inch  telescope  itself. 
The  silvered  concave  mirror  was  made  in  the  optical  shop  by  Mr.  Ritchey,  who 
also  supervised  the  construction  of  the  mounting  in  the  Observatory  machine 


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THE  YERKES  OBSERVATORY 


II 


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12 


THE  UNIVERSITY  OF  CHICAGO 


Fig.  6. — The  Sun,  Photographed  with  the  Spectroheliograph  on 
August  12,  1903  (Hale  and  Ellerman) 

The  white  blotches  are  areas  of  intensely  brilliant  calcium  vapor,  which  would 
be  invisible  on  an  ordinary  photograph. 


shop.  The  figure  of  the  mirror  is  very  perfect,  and  remarkably  fine  photo¬ 
graphs  of  nebulae  have  been  obtained  with  it,  principally  by  Mr.  Ritchey. 
It  has  the  great  advantage  over  a  refractor  that  the  rays  of  all  colors  are  united 
in  the  same  focus,  here  8  feet  from  the  surface  of  the  mirror.  A  star  of  the 
ninth  magnitude  (having  less  than  one-thousandth  of  the  brightness  of  a  first- 
magnitude  star)  can  be  photographed  with  it  in  one  second,  and  the  instru¬ 
ment  is  exclusively  used  photographically.  With  an  exposure  of  three  hours 
vast  numbers  of  stars  will  impress  their  images  on  the  plate,  many  of  which 
cannot  be  seen  at  all  with  the  40-inch  refractor.  Some  work  on  stellar  spectra 
has  also  been  done  with  the  instrument. 

The  northeast  dome  contains  the  Kenwood  equatorial  refractor  of  1 2  inches 
aperture,  which,  together  with  much  valuable  equipment,  was  given  to  the 
University  by  Mr.  William  E.  Hale  and  Mr.  George  E.  Hale,  and  moved  here 


THE  YERKES  OBSERVATORY 


13 


Fig.  7, — Composite  or  Two  Plates  Made  on  August  14,  1907  (Fox) 
Showing  calcium  vapor  as  prominences  at  sun’s  edge  and  on  the  disk 

from  its  former  location  at  their  residence  in  Chicago.  The  instrument  has 
two  objectives,  one  for  visual  work,  the  other  for  photography,  both  made  by 
Mr.  J.  A.  Brashear.  The  mounting  is  by  Warner  &  Swasey.  An  excellent  filar 
micrometer,  by  the  last-named  firm,  was  purchased  for  this  telescope  in  1906. 
The  old  stellar  spectrograph,  provided  by  Mr.  Yerkes  in  the  original  equipment 
for  the  40-inch  telescope,  has  recently  been  adapted  for  use  in  solar  spectroscopy 
with  the  12-inch  telescope.  The  telescope  has  been  used  for  observations  of 
comets,  double  stars,  variable  stars,  for  direct  photographs  of  the  sun,  stellar 
photometry,  etc.  A  modern  twin  mounting  is  urgently  needed. 

On  the  main  roof,  between  the  two  small  domes,  is  housed  the  Brashear 
comet-seeker,  of  six  inches  aperture.  A  small  camera  is  also  installed  here  to 
serve  as  sky-patrol.  In  the  meridian  room  at  the  east  end  of  the  building  is 
located  the  broken- tube  transit  of  3  inches  aperture,  made  in  the  machine  shop. 

At  the  north  window  of  the  short  corridor  leading  to  the  meridian  room  are 
the  barometer,  maximum  and  minimum  thermometers,  and  the  thermograph. 
Observations  are  made  twice  a  day.  A  thermograph  is  installed  on  the  north 
side  of  the  great  dome  on  the  outside  balcony.  A  shelter,  of  the  United  States 
Weather  Bureau’s  pattern,  containing  maximum  and  minimum  thermometers, 
was  placed  on  the  lawn  in  1917.  No  seismographs  for  recording  earthquakes, 
nor  instruments  for  determining  the  state  of  the  earth’s  magnetism,  are  main¬ 
tained  at  the  Observatory. 


14 


THE  UNIVERSITY  OF  CHICAGO 


In  an  upper  room  has  been  set  up  an  apparatus  devised  by  Professor  Hale 
by  which  the  photographs  of  the  sun  taken  with  the  spectroheUograph  can  be 
optically  projected  upon  a  steel  globe  ruled  with  parallels  and  meridians,  so 
that  the  positions  of  significant  markings  on  the  sun  can  be  easily  read  off 
without  trigonometrical  computation. 

An  important  adjunct  of  an  astrophysical  observatory  is  its  spectroscopic 
laboratory,  where  experiments  may  be  made  to  match  in  some  degree  the  con¬ 
ditions  found  in  celestial  objects,  in  running  to  earth  unknown  elements  in  their 
spectra,  and  in  various  researches  calculated  to  assist  in  the  interpretation  of  the 
phenomena  of  the  heavenly  bodies.  Unfortunately  it  has  not  been  possible  to 
obtain  funds  for  keeping  a  physicist  steadily  employed.  During  two  or  three 
years,  principally  from  a  gift  of  about  $4,000  made  by  Mr.  Yerkes,  such  work 
was  in  progress.  Extensive  studies  were  made  by  Mr.  N.  A.  Kent,  in  collabora¬ 
tion  with  IMr.  Hale,  on  the  effect  of  heavy  pressure  upon  the  spectrum  of  the 
spark;  by  IMr.  Kent  on  the  comparison  of  w^ave-length  in  the  spectnun  of  the 
same  element  when  rendered  luminous  in  the  spark  and  in  the  arc,  and  by 
Mr.  H.  M.  Reese  on  the  enhanced  lines  in  spark  spectra.  A  large  spectrome¬ 
ter  by  Fuess  has  recently  been  added  to  the  equipment  of  this  laboratory. 

In  view  of  the  very  general  use  of  photography  in  modern  astronomy,  a 
laboratory  for  photographic  research  is  important  for  an  institution  like  this. 
In  the  years  from  1903  to  the  end  of  1908  such  a  laboratory  was  in  successful 
operation  under  the  charge  of  Mr.  R.  J.  Wallace.  Particularly  during  the 
years  1905-8,  under  a  grant  to  the  Observatory  from  Mr.  George  Eastman,  of 
Rochester,  New  York,  Mr.  Wallace  was  able  to  devote  his  time  to  research  on 
various  problems  in  photography,  including  the  adaptation  and  sensitization 
of  plates  for  particular  purposes.  Aside  from  the  improvement  of  the  photo¬ 
graphic  routine  in  the  different  departments  of  the  Observatory,  these  investi¬ 
gations  resulted  in  important  papers  published  in  the  Astrophysical  Journal 
and  elsewhere. 

The  great  optical  works  at  Jena,  having  the  firm-name  Carl  Zeiss,  have 
rendered  great  service  in  the  development  of  microscopes  and  apparatus  for 
measuring  photographs.  Several  are  owned  by  the  Observatory,  the  most 
important  being  known  as  the  “Stereo-comparator”  and  “Blink-mikroskop,” 
purchased  in  1907.  This  is  a  massive  instrument  in  which  two  different  nega¬ 
tives  can  be  examined,  either  at  the  same  time  or  in  instantaneous  succession, 
so  that  any  change  in  position,  size,  or  intensity  of  the  images  is  at  once  notice¬ 
able  to  the  eye,  and  discoveries  are  greatly  facilitated.  Accurate  measure¬ 
ments  of  various  kinds  can  also  be  made  with  this  apparatus.  Another  valu¬ 
able  accessory  is  the  Hartmann  spectro-comparator,  acquired  at  ihe  same  time, 
with  which  two  negatives  of  spectra  can  be  simultaneously  compared  and 
measured  against  each  other.  Several  other  measuring  machines,  some  of 
them  made  in  the  Observatory  shop,  are  in  use  for  the  precise  study  of  plates. 
In  the  computing  room,  calculating  machines  made  in  Europe,  capable  of 
handling  18  figures,  are  principally  employed  for  multiplication  and  division. 


THE  YERKES  OBSERVATORY 


15 


Fig.  8. — The  24-lNCH  Reflector,  Occupying  the  Southeastern  Dome 

The  silvered  glass  mirror  was  made  by  Mr.  Ritchey  in  the  optical  shop,  the 
mounting  in  the  machine  shop,  of  the  Observatory.  It  will  photograph  stars  which 
cannot  be  seen  with  the  great  refractor. 


i6 


THE  UNIVERSITY  OF  CHICAGO 


Fig.  9. — The  Great  Nebula  in  Orion,  Photographed  with  the  24-lNCH 
Reflector  (Ritchey) 

This  inconceivably  large  mass  of  gas,  chiefly  hydrogen,  helium,  and  nebulum 
(not  yet  found  in  the  earth),  is  a  feature  of  the  constellation  Orion. 

As  the  original  equipment  of  the  Observatory  was  chiefly  limited  to  the 
40-inch  and  12-inch  telescopes,  much  remained  to  be  done  in  fitting  out  the 
institution  for  its  best  efiflciency.  The  Trustees  of  the  University  adopted 
the  important  recommendation  of  the  Director  and  provided  from  the  start 
for  maintaining  an  instrument-maker  and  machine  shop,  the  machines  of 
which  were  chiefly  donated  from  the  Kenwood  Observatory.  In  this  way  the 
equipment  has  been  gradually  increased,  kept  in  repair,  and  perfected.  At 
times,  when  special  gifts  were  available,  three  men  have  been  employed  in  the 
shop.  The  principal  apparatus  constructed  have  been  these:  the  two-foot 
reflector,  the  Snow  horizontal  telescope,  the  Bruce  spectrograph,  the  transit 
instrument,  a  spectrohehograph,  a  coelostat  for  eclipse  use,  a  quartz  spectro¬ 
graph  for  the  two-foot  reflector,  and  many  smaller  instruments  and  attach¬ 
ments.  In  the  carpenter  shop  a  great  number  of  patterns  have  been  made,  and 


THE  YERKES  OBSERVATORY 


17 


Fig.  10. — Nebula  in  Triangulum  (Messier  33),  Photographed  with  the  24-lNCH 

Reflector  (Ritchey) 

The  spiral  structure  can  readily  be  seen.  Its  distance  from  the  earth  is  not 
less  than  that  of  the  surrounding  stars,  which,  it  should  be  recalled,  are  all  suns,  pre¬ 
sumably  not  smaller  and  perhaps  much  larger  than  our  own  sun. 


i8  THE  UNIVERSITY  OF  CHICAGO 


special  cabinets  of  various  kinds  have  been  constructed  for  negatives,  charts, 
and  other  valuable  records. 

HORIZONTAL  TELESCOPE 

Owing  to  the  great  convenience  of  operation  of  a  horizontal  coelostat  tele¬ 
scope  for  solar  work  where  massive  spectroheliographs  must  be  attached  and 
removed,  Mr.  Hale  early  began  the  construction  of  such  an  instrument.  The 
first  one  had  barely  been  completed,  in  a  temporary  wooden  and  paper  struc¬ 
ture  outside  of  the  Observatory,  when  it  was  burned  (December  22,  1902)  from 
the  sparks  of  the  high-potential  apparatus  used  for  the  comparison  spectrum. 
A  30-inch  plane  mirror  and  a  24-inch  concave  mirror,  made  in  the  optical  shop, 
were  destroyed,  together  with  the  driving-clock  and  all  but  the  heavy  castings 
of  the  coelostat.  A  few  months  later  Miss  Helen  M.  Snow,  of  Chicago,  made  a 
gift  of  $10,000  in  honor  of  her  father,  the  late  George  W.  Snow,  for  reconstruct¬ 
ing  the  instrument.  A  wooden  building  was  erected  600  feet  north  of  the 
Observatory,  and  by  great  activity  in  the  optical  and  machine  shops  it  was 
possible  formally  to  open  the  Snow  telescope  in  October,  1903. 

Having  been  interested  in  the  possibilities  of  solar  research  under  the  more 
perfect  atmospheric  conditions  of  southern  California,  Mr.  Hale,  in  the  next  year, 
obtained  a  grant  of  $10,000  from  the  Carnegie  Institution  of  Washington  for  an 
expedition  for  solar  research  from  the  Yerkes  Observatory  to  Mount  Wilson, 
California.  The  Snow  telescope  was  safely  transported  thither  and  mounted 
in  a  steel  and  canvas  building,  which  experience  showed  to  be  more  suitable 
than  the  wooden  structure.  The  results  obtained  were  so  satisfactory  and  so 
promising  for  the  future  that  the  Carnegie  Institution  decided  to  establish 
its  own  observatory  there.  An  arrangement  satisfactory  to  the  donor  and  all 
others  interested  was  later  made  whereby  the  Snow  telescope  was  purchased 
by  the  Solar  Observatory,  the  money  thus  returned  to  the  University  of  Chicago 
being  used  to  buy  the  stereo-comparator,  and  $5,000  being  established  as  the 
Snow  fund,  from  the  interest  of  which  instrumental  equipment  can  be  pur¬ 
chased.  This  was  the  first  endowment  fund  provided  specifically  for  the  use 
of  the  Observatory.  In  this  connection  it  may  be  stated  that  in  his  will  Mr. 
Yerkes  made  a  bequest  for  the  maintenance  of  the  Observatory  of  $100,000, 
a  portion  of  which  was  received  from  his  estate  in  1913. 

In  1908  the  eclipse  coelostat  was  mounted  in  the  Snow  building  in  con¬ 
nection  with  an  autocollimating  spectrograph,  and  a  powerful  instrument  for 
research  in  the  solar  spectrum  was  secured  at  small  additional  cost. 

BRUCE  PHOTOGRAPHIC  TELESCOPE 

In  1897,  in  response  to  a  presentation  of  the  advantages  of  such  an  instru¬ 
ment  by  Mr.  Barnard,  Miss  Catherine  W.  Bruce,  of  New  York,  placed  in  his 
hands,  as  a  gift  to  the  University  of  Chicago,  the  sum  of  $7,000  for  the  con¬ 
struction  of  a  telescope  especially  designed  for  the  photography  of  the  large 
areas  and  extended  objects  in  the  sky,  particularly  the  Milky  Way  and  comets — 
a  field  in  which  Mr.  Barnard  has  been  a  particularly  successful  pioneer.  A 


THE  YERKES  OBSERVATORY 


19 


number  of  years  were  spent  in  the  endeavor  to  secure  a  lens  which  should  fully 
meet  the  ideal  requirements.  A  fine  lo-inch  doublet,  constructed  by  Brashear, 
was  finally  accepted,  in  1900,  and  a  special  mounting  was  designed  and  built 
by  Warner  &  Swasey.  The  instrument  was  set  up  in  April,  1904,  in  a  neat 
wooden  building  (erected  from  interest  on  the  Bruce  fund),  350  feet  southwest 
of  the  great  dome  of  the  Observatory.  In  addition  to  the  lo-inch  (focal 
length,  50  inches)  the  mounting  also  carries  a  6|-inch  Voigtlander  doublet,  a 
5-inch  visual  guiding  telescope,  and  generally  a  3|-inch  portrait  lens.  Many 
photographs  of  the  Milky  Way,  showing  good  definition  over  a  field  of  50 
square  degrees,  have  been  obtained  by  Mr.  Barnard.  In  1905  he  spent  nine 
months  at  Mount  Wilson  (altitude  nearly  6,000  feet)  in  photographing  the  Milky 
Way,  particularly  those  southern  portions  not  to  be  reached  at  Lake  Geneva. 
This  trip  was  made  possible  by  a  grant  from  Mr.  J.  D.  Hooker,  of  Los  Angeles. 
The  Carnegie  Institution  of  Washington  has  lately  made  a  grant  for  the  purpose 
of  publishing  an  atlas  of  reproductions  of  these  pictures  of  the  Milky  Way, 
and  the  work  is  now  in  progress.  Of  the  comet  Morehouse,  discovered  on 
plates  taken  with  the  Bruce  telescope  by  Mr.  Morehouse  on  September  i, 
1908,  Mr.  Barnard  secured  no  less  than  350  negatives. 

ZEISS  ULTRA-VIOLET  CAMERA 

Another  photographic  lens  of  special  value  is  the  Zeiss  doublet,  made  of 
glass  particularly  transparent  to  ultra-violet  rays,  of  5.7  inches  aperture  and 
32  inches  focal  length.  The  stellar  images  it  produced  when  slightly  out  of 
focus  were  found  to  be  disks  of  remarkably  uniform  intensity.  By  measuring 
the  intensity  of  these  disks  under  the  Hartmann  “surface  photometer”  Mr. 
Parkhurst  has  attained  an  exceedingly  high  degree  of  accuracy  in  stellar 
photometry.  Photographs  taken  with  an  exposure  of  twenty  minutes,  with 
wire  gratings  placed  over  the  objective,  give  measurable  focal  images  for 
photometric  purposes  of  thirteenth-magnitude  stars. 

Objective-prisms  of  the  same  transparent  glass  and  with  the  same  aperture 
as  the  lens,  with  refracting  angles  of  1 5°  and  30°,  respectively,  are  provided 
for  the  doublet.  They  make  possible  the  study  of  the  spectra  of  all  the  stars 
which  are  within  the  field  of  view.|^This  apparatus  has  proved  to  be  particularly 
useful  for  photographing  the  spectra  of  comets. 

This  important  instrument  has  heretofore  been  used  provisionally  on  a 
mounting  belonging  to  Mr.  Parkhurst  and  in  a  temporary  building  located 
1,000  feet  north  of  the  Observatory.  It  will  be  transferred  to  a  new  small 
dome  to  be  erected  on  the  Observatory  grounds  northeast  of  the  main  building 
as  soon  as  the  necessary  funds  can  be  secured. 

The  power-house,  which  also  furnishes  the  steam  heat  (largely  exhaust) 
for  the  main  building,  is  situated  about  750  feet  northeast  from  the  center  of 
the  large  dome.  It  was  included  in  the  original  gift  of  Mr.  Yerkes.  Its  equip¬ 
ment  consists  of  duplicate  boilers,  and  an^SXio  Ideal  engine,  directly  con¬ 
nected  with  a  Siemens  &  Halske  dynamo,  of  capacity  200  amperes  at  125 
volts,  which  furnishes  current  Jor  the  motors  in  the  shops,  for  the  great 


20 


THE  UNIVERSITY  OF  CHICAGO 


Fig.  II. — The  Bruce  Photographic  Telescope  as  Temporarily  Set  up  in  the 
Corridor  of  the  Yerkes  Observatory 

It  is  now  located  in  the  small  dome  to  the  southwest  of  the  Observatory. 
With  this  Professor  Barnard  has  obtained  many  unsurpassed  photographs  of  the 
Milky  Way  and  of  comets. 


THE  YERKES  OBSERVATORY 


21 


Fig.  12. — A  Small  Portion  of  the  Milky  Way  in  Cepheus,  Photographed  with 
THE  Bruce  Telescope  on  September  ii,  1904  (Barnard) 

Exposure  6  Hours  and  40  Minutes 

As  will  be  seen  in  this  picture,  the  Milky  Way  consists  of  innumerable  faint  stars 
(in  reality  distant  suns)  separately  indistinguishable  with  the  naked  eye,  which  are 
distributed  irregularly  in  the  sky.  Only  three  or  four  of  the  stars  on  this  plate  can 
be  seen  with  the  naked  eye. 


22 


THE  UNIVERSITY  OF  CHICAGO 


dome  and  rising  floor,  for  the  30-foot  dome,  and  for  all  the  general  lighting 
and  dark-room  lamps  of  the  Observatory.  The  water  for  all  purposes  of  the 
institution  is  obtained  from  the  lake  by  an  electric  pump  at  the  shore  operated 
by  current  from  the  power-house,  and  is  stored  in  a  30,000-gallon  tank  near 
the  power-house. 

Questions  are  so  often  raised  as  to  the  cost  of  the  equipment  that  a  brief 
statement  may  be  given  here.  The  land  originally  given  was  valued  at  $30,000. 
The  cost  of  the  completed  object-glass  of  the  great  refractor  was  $66,000;  of 
the  telescope  mounting  itself,  $55,000;  of  the  dome  and  rising  floor,  $45,000, 
and  of  the  remainder  of  the  Observatory  building,  including  the  southeast 
dome  and  the  power-house  and  its  equipment,  about  $150,000.  The  instru¬ 
ments  and  equipment  of  the  Kenwood  Observatory,  with  its  dome,  the  gift 
of  Mr.  William  E.  Hale  and  his  son,  were  valued  at  $30,000.  The  Bruce 
telescope  and  building  cost  about  $8,000;  the  Snow  telescope  and  building, 
$10,000.  About  $15,000  have  thus  far  been  spent  on  grading  and  planting. 

In  response  to  the  numerous  calls  for  lantern  slides,  transparencies,  and 
prints  from  astronomical  negatives  made  at  this  Observatory,  it  became 
necessary  several  years  ago  to  arrange  for  supplying  them  to  teachers,  lecturers, 
and  others  interested.  A  photographer  is  employed  in  preparing  these  repro¬ 
ductions,  which  are  sold  at  a  price  to  cover  their  cost,  through  the  medium 
of  the  University  of  Chicago  Press.  A  catalogue  of  such  slides,  etc.,  including 
a  total  of  about  800  subjects,  has  been  printed,  and  is  sent  on  request  by  the 
University  of  Chicago  Press. 

PUBLICATIONS 

Current  results  of  investigations  at  the  Observatory  are  published  in  various 
journals,  American  and  foreign.  Those  of  an  astrophysical  character  gener¬ 
ally  appear  in  the  Astrophysical  Journal,  of  which  the  director  of  the  Observa¬ 
tory  is  the  editor,  published  ten  times  a  year  by  the  University  of  Chicago 
Press.  The  Carnegie  Institution  of  Washington  has  published  several  separate 
volumes  by  members  of  the  staff,  two  of  which  have  already  been  referred  to. 
Others  are:  Researches  in  Stellar  Photometry  by  J.  A.  Parkhurst;  The  Rotation 
Period  of  the  Sun  by  George  E.  Hale  and  Philip  Fox;  Measures  of  Proper 
Motion  Stars  by  S.  W.  Burnham.  Prior  to  1916  the  University  had  not  been 
able  to  provide  a  regular  fund  for  the  issue  of  the  formal  quarto  Publications 
of  the  Yerkes  Observatory,  and  these  are  therefore  much  in  arrears.  The 
volumes  so  far  issued  are:  I  (1900),  pp.  296,  A  General  Catalogue  of  i,2go 
Double  Stars  Discovered  from  i8yi  to  i8gg,  by  S.  W.  Burnham.  H  (1904), 
pp.  413,  papers  by  Messrs.  Burnham;  Barnard;  F.  R.  Moulton;  Frost  and 
Adams;  Hale,  Ellerman,  and  Parkhurst;  Ritchey;  and  Laves.  HI,  Parts  i 
and  2  (1903),  by  Hale  and  Ellerman,  and  Hale  and  Kent.  IV,  Part  i  (1917),  by 
Slocum,  Mitchell,  Lee,  Joy,  and  VanBiesbroeck;  Part  2  (1918),  by  E.  P.  Hubble; 
Part  3  (1920),  by  Van  Biesbroeck  and  ]\lrs.  Pettit.  Part  3  of  Vol.  HI,  by 
Fox,  is  in  press  (1921). 


THE  YERKES  OBSERVATORY 


23 


Fig.  13. — Halley’s  Comet  as  Photographed  with  Bruce  Telescope 
ON  May  29,  1910  (Barnard) 

The  plate  was  exposed  for  two  hours.  The  observer  kept  the  telescope  constantly 
pointed  on  the  comet,  following  its  motion  among  the  stars,  which  caused  the  elonga¬ 
tion  of  the  star  images.  The  tail  of  the  comet,  as  shown  on  this  plate,  was  about 
7  million  miles  long.  It  was  composed  ot  luminous  vapors,  chiefly  hydrocarbons. 


3  0112105737750 

24  THE  UNIVERSITY  OF  CHICAGO 


INSTRUCTION 

Undergraduate  instruction  in  astronomy  is  not  given  at  the  Observatory. 
This  is  provided  at  the  University,  together  with  thorough  courses  in  theoretical 
astronomy  and  celestial  mechanics  taught  by  Professors  Moulton,  Laves,  and 
MacMillan.  Graduate  students  competent  in  observational  work  in  astron¬ 
omy  and  astrophysics  are  welcome  and  may  become  Fellows  under  the  usual 
University  regulations.  All  candidates  for  the  Doctor’s  degree  in  the  depart¬ 
ment  are  required  to  work  at  the  Observatory  at  least  for  one  quarter. 
Astronomers  from  other  institutions  often  come  as  volunteer  research  assist¬ 
ants.  The  Astronomical  Club  meets  frequently  for  discussions. 

The  Observatory  library  contains  at  present  over  6,ooo  volumes  and  5,000 
pamphlets.  About  80  scientific  magazines  and  journals  are  regularly  received, 
principally  in  exchange  for  the  Astrophysical  Journal. 

The  pressure  for  time  for  their  scientific  use  has  made  it  impossible  to  per¬ 
mit  visitors  to  see  through  the  telescopes.  Opportunity  is  given,  however, 
for  them  to  inspect  the  Observatory  and  the  great  refractor,  on  Saturdays: 
from  June  i  to  September  30  between  i :  30  and  4 : 30  p.m.  ;  during  the  remainder 
of  the  year,  between  10  and  12  a.m.  A  member  of  the  staff  demonstrates  the 
operation  of  the  large  telescope  and  explains  the  work  of  the  Observatory. 
Interesting  astronomical  photographs  are  displayed  in  the  corridors.  Several 
thousand  visitors  annually  avail  themselves  of  this  opportunity. 

The  staff  of  the  Observatory  is  constituted  as  follows  (1921-22): 

Edwin  B.  Frost,  Professor  of  Astrophysics,  and  Director. 

Edward  E.  Barnard,  Professor  of  Practical  Astronomy. 

John  A.  Parkhurst,  Associate  Professor  of  Practical  Astronomy. 

Storrs  B.  Barrett,  Assistant  Professor  of  Astrophysics,  Secretary,  Librarian. 
George  Van  Biesbroeck,  Assistant  Professor  of  Practical  Astronomy. 
Oliver  J.  Lee,  Instructor  in  Practical  Astronomy. 

J.  Paraskevopoulos  (of  Athens),  Volunteer  Research  Assistant  (1919-21). 
Ernest  C.  Bryant  (Middlebury),  Clifford  C.  Crump  (Ohio  Wesleyan), 
Charles  E.  Rogers  (Trinity),  Volunteer  Research  Assistants  (Summer 
1921). 

Otto  Struve,.  Assistant  in  Stellar  Spectroscopy. 

Mary  R.  Calvert,  Computer. 

Florence  B.  Lee,  Office  Secretary. 

Harriet  McW.  Parsons,  Fellow  (1920-21). 

Elsie  Johnson,  Lela  Cable,  Esther  Searles,  Temporary  Computers. 
George  C.  Blakslee,  Photographer. 

Frank  R.  Sullivan,  Engineer  in  charge  of  40-inch  telescope. 

Stephen  A.  Stam,  Instrument  Maker. 

Henry  M.  Foote,  Carpenter,  and  Supervisor  of  Building. 

Diedrich  j.  Oetjen,  Engineer  at  Power  House. 

Wm.  Koeppen,  Night  Engineer  at  Power  House. 

Carl  I.  Wendell,  Janitor. 

Carl  Bertelson,  Gardener. 


